[SCSI] libiscsi, iscsi_tcp: check suspend bit before each call to xmit_task

If we had multiple tasks on the cmd or requeue  lists, and iscsi_tcp
returns a error, the write_space function can still run and queue
iscsi_data_xmit. If it was a legetimate problem and iscsi_conn_failure
was run but we raced and iscsi_data_xmit was run first it could miss
the suspend bit checks, and start trying to send data again and hit
another timeout. A similar problem is present when using cxgb3i.

This has libiscsi check the suspend bit before calling the xmit
task callout, so we at least do not try sending multiple tasks
(one could be sent).
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/scsi/libiscsi.c

@@ -1280,6 +1280,9 @@ static int iscsi_xmit_task(struct iscsi_conn *conn)
 	struct iscsi_task *task = conn->task;
 	int rc;
 
+	if (test_bit(ISCSI_SUSPEND_BIT, &conn->suspend_tx))
+		return -ENODATA;
+
 	__iscsi_get_task(task);
 	spin_unlock_bh(&conn->session->lock);
 	rc = conn->session->tt->xmit_task(task);
@@ -1329,7 +1332,7 @@ static int iscsi_data_xmit(struct iscsi_conn *conn)
 	int rc = 0;
 
 	spin_lock_bh(&conn->session->lock);
-	if (unlikely(conn->suspend_tx)) {
+	if (test_bit(ISCSI_SUSPEND_BIT, &conn->suspend_tx)) {
 		ISCSI_DBG_SESSION(conn->session, "Tx suspended!\n");
 		spin_unlock_bh(&conn->session->lock);
 		return -ENODATA;
@@ -1338,7 +1341,7 @@ static int iscsi_data_xmit(struct iscsi_conn *conn)
 	if (conn->task) {
 		rc = iscsi_xmit_task(conn);
 	        if (rc)
-		        goto again;
+		        goto done;
 	}
 
 	/*
@@ -1358,7 +1361,7 @@ check_mgmt:
 		}
 		rc = iscsi_xmit_task(conn);
 		if (rc)
-			goto again;
+			goto done;
 	}
 
 	/* process pending command queue */
@@ -1379,14 +1382,14 @@ check_mgmt:
 				list_add_tail(&conn->task->running,
 					      &conn->cmdqueue);
 				conn->task = NULL;
-				goto again;
+				goto done;
 			} else
 				fail_scsi_task(conn->task, DID_ABORT);
 			continue;
 		}
 		rc = iscsi_xmit_task(conn);
 		if (rc)
-			goto again;
+			goto done;
 		/*
 		 * we could continuously get new task requests so
 		 * we need to check the mgmt queue for nops that need to
@@ -1412,16 +1415,14 @@ check_mgmt:
 		conn->task->state = ISCSI_TASK_RUNNING;
 		rc = iscsi_xmit_task(conn);
 		if (rc)
-			goto again;
+			goto done;
 		if (!list_empty(&conn->mgmtqueue))
 			goto check_mgmt;
 	}
 	spin_unlock_bh(&conn->session->lock);
 	return -ENODATA;
 
-again:
-	if (unlikely(conn->suspend_tx))
-		rc = -ENODATA;
+done:
 	spin_unlock_bh(&conn->session->lock);
 	return rc;
 }